Which EXIF tag should I set for 35mm-equivalent focal length on a manual lens?

Asked 1/12/2015

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I’m adding EXIF data with ExifTool to photos shot on a Canon 60D using a manual Rokinon 8mm f/3.5 fisheye. I can set FocalLength to 8mm, but I’m unsure whether I should also write a 35mm-equivalent focal length tag.

I found FocalLengthIn35mmFormat, but files from an electronically connected Canon EF-S lens don’t always contain that tag, even though ExifTool still reports a composite 35mm-equivalent focal length. Should I write FocalLengthIn35mmFormat, or is it better to rely on the camera’s existing focal-plane metadata and only set FocalLength?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

11y ago

2 Answers

3

Good practice is adding

0x920a Focal length
0x9205 Max Aperture Value
0xa405 Focal Length In 35mm Format (60D sensor active area has 26.82mm diagonal)
0xa432 Lens Info
0xa433 Lens Make
0xa434 Lens Model

Originally by user28381. Source · Licensed CC BY-SA 4.0

user28381

11y ago

0

AI Answer

Generated from our catalog & community — verify before relying on it.

For a manual lens, the key tag to write is FocalLength. On a Canon 60D, ExifTool can derive the 35mm-equivalent focal length from FocalLength plus the camera’s existing focal-plane resolution/size metadata, which the body records even with manual lenses.

So if your goal is to stay consistent with how Canon files normally look, you generally do not need to write FocalLengthIn35mmFormat yourself.

Useful tags to add for a manual lens are:

  • FocalLength
  • MaxApertureValue
  • LensInfo
  • LensMake
  • LensModel

You can also add FocalLengthIn35mmFormat if you want, but it isn’t necessary for ExifTool to show the 35mm equivalent. Writing focal-plane size tags is not the better approach here; those are camera-derived values and may vary with things like digital zoom. In short: set FocalLength, and let the equivalent focal length be calculated from the camera metadata already present.

UniqueBot

AI

11y ago

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